Hydraulic pressure-proportioning means



June 12,' 1956 W, G, WHEELER ET AL 2,749,711

'HYDRAULEC PRESSURE-PROPORTIONING MEANS Filed Dec. 14, 1955 :inventors @Homey United States Patent O HYDRAULIC PRESSURE-PROPORTIONING MEANS Walter G. Wheeler, Los Angeles, and David C. Kramer, Redondo Beach, Calif., assignors to Richard Seifried, Playa Del Rey, Calif.

Application December 14, 1953, Serial No. 398,018

6 Claims. (Cl. 60-97) This invention relates to means to proportion the pressure among a bank of hydraulic cylinders so that a cornmon member connected to or inlluenced by said banks of cylinders has intermediate force or forces applied thereto that are between or the average of the forces applied to the ends thereof. This application is a continuation-inpart of our pending application, Serial No. 301,024, led July 26, 1952, and issued on April 27, 1954, as Patent No. 2,676,638.

An object of the present invention is to provide means, as indicated, to apply hydraulic force upon a common member which is proportional at intermediate parts of said member to the forces applied at the ends thereof. An example of such member is the jaw connected to an edge of a metal sheet that has a tapered thickness and to be stretch-formed over a die. Thus, there are different force requirements at the opposite ends of the sheet and of the jaws that grip the edges of such a sheet. Since stress is equal to the force per unit area, in Vorder to maintain the same stress along a sheet that has varying thickness, the force must vary. To vary the force exerted by a bank of hydraulic cylinders, the pressure in said cylinders must vary accordingly. ln this invention, the pressures used at two points of application are proportioned and applied to other points.

The invention also has for its objects to provide such means that are positive in operation, convenient in use, easily installed in a working position and easily disconnected therefrom, economical of manufacture, relatively simple, and of general superiority and serviceability.

The invention also comprises novel details of construction and novel combinations and arrangements of parts, which will more fully appear in the course of the following description. However, the drawing merely shows and the following description merely describes, preferred embodiments of the present invention, which are given by way of illustration or example only.

ln the drawing, like reference characters designate similar parts in the several views.

Fig. 1 is a diagrammatic View of hydraulic pressureproportioning means according to the present invention.

Fig. 2 is a fragmentary diagrammatic View of a modification. v

Fig. 3 is a schematic sectional View of one form of pressure-relief valve used in the present means.

ln the drawing, the member 5 represents an element on which hydrauiic force is to be applied at three points 6, 7 and 3 by the piston rods of respective hydraulic units 9, 16 and 11 which are each here shown as a cylinder 12, a piston 13 in each cylinder and a piston rod or stem 14 extending from one end of each said cylinder. Hydraulic pressure fluid is conducted to the cyiinders of the units 9, and 11 by respective pipes 15, 16 and 17.

While the above assembly of elements may be used in other connections, the same is especially devised to apply a retractive force on member 5 according to the resistance to retraction of said member. Thus, assuming mem- "ice ber S to be an elongated jaw in which one end of a sheet 18 is clamped and it is desired to stretch said sheet more at edge 19 than at opposite edge 20 and to stretch the middle portion 21 of said sheet proportionally to the stretch at the edges, the present pressure-proportioning means 22 is connected to pipes 15, 16 and 17 to provide in unit 11: (l) an average of the forces applied by units 9 and 10, if the variation in forces on sheet 18 is uniform; or (2) a proportionate force that is between the forces applied by units 9 and 10, if the variation in forces on sheet 18 is not uniform.

In the form of Fig. l, the pressure-proportioning means 22 comprises, generally, pressure-dividing apparatus 23 controlled by pres-sure in pipes 15 and 16 by way of pipes 24 and 25 connected, respectively, to pipes 15 and 16,- a pressure relief valve Z6 connected to pipe 17, and an outlet pipe 27 between apparatus 23 and said relief valve 26 to regulate the latter according to the pressure output of apparatus 23.

The pressure-dividing apparatus 23 comprises two cylinders 28 and 29 arranged in tandem with their respective pistons 30 and 31 on a common stem 32. The pipe 2d connects to cylinder 28 and the pipe 25 to cylinder 29, both connections being on the same end of both cylinders. The dividing apparatus 23 further includes a cylinder 33, an exhaust pipe 34 interconnecting the latter cylinder and the opposite ends of cylinders 28 and 29, a piston 35 in cylinder 33 and a stem 36a extending from said piston 35 in generally parallel relation to stem 32 and in the same direction.

A lever 36 is arranged on a fulcrum 37 that divides said lever into arms 38 and 39 which are respectively engaged with the ends of piston stems 32 and 36a. In the drawing, the fulcrum 37 is arranged so that arm 3S is half the length of arm 39. By shifting the fulcrum to pass through one or another of the holes 46 in lever 36, the length ratios of arms 38 and 39 may be varied, as desired.

The pipe 27 extends from cylinder 33, at the end that is opposite to where exhaust pipe 34 is connected, to the pressure relief valve 26. The latter is of the type that is regulatable, the pressurized fluid in pipe 27 providing a variable pressure that regulates the valve which, by way of an exhaust pipe 41, varies the pressure in pipe 17 according to the relief regulation of said valve 26.

The pressures supplied through pipes 15 and 16 to the chambers 42 and 43 of the respective hydraulic unit-s 9 and 10 create commensurate retractive forces on stems 14 of said units and on respective points 6 and 7 of members 5. Whether the same or different, the pressures in pipes 15 and 16 are each effective on pistons 3) and 31, respectively. Thus, the sum of these pressures is effective on stem 32 and the force thereof is represented by the arrow 4d. lf, as shown, lever arms 38 and 39 are at a one-to-two ratio, the force received by shorter arm 3S is transmitted by longer arm 39 as a force, represented by arrow 45, that is one-half the force produced on stem 32. Although travelling twice the distance that stem 32 travels, stern 36a, through its piston 35, exerts a pressure in chamber 46 of cylinder 33 that is one-half the sum of the pressures in chambers 47 and 48 of cylinders 29 and 30, respectively. This is the average of the pressures supplied to units 9 and 10. A pressure between the pressures in pipes 15 and 16, but not necessarily the average thereof, may be obtained in chamber 46 in magnitude according to the position of fulcrum 37 and changeA the ratio of the lever arms. Pipe 27 conducts the pressure of chamber 46 to relief valve 26.

As shown in Fig. 3, the valve 26 comprises a cylinder 55 to which pipes 17 and 41 are connected, a piston 56 operating in said cylinder to control pressure ilow between said pipes. Thus, when piston 56 is retracted toward the right, as in Fig. 3, the ow from pipe 17 to relief pipe 41 is un-throttled and the pressure in pipe 17 remains constant. However, when the piston 56 is moved toward the left, the degree of closure thereby of inlet to relief line 41, throttles the flow accordingly, and results in a corresponding pressure increase in pipe 17.

Movement of piston 56 toward the left results from movement toward the left induced on piston 57 in cylinder 58 by the pressure in pipe 27.

As the relief pipe 41 is being closed and the pressure in pipe 17 increases, the pressure in chamber S9 increases accordingly and this increased pressure is manifested on piston 60 through pipe connection 61. Since pistons 57, 56 and 60 are connected rigidly to each other, the pressure on piston 60 will be in opposition to the pressure on piston S7. When these two pressures become equal, a state of balance will be achieved in which movement of lever 36 stops and the now increased pressure in pipe 17 is produced in chamber 47a of hydraulic unit 11.

Pipe 27 is connected to said valve 26 so that the pressure delivered by said pipe increases or decreases the ability of the valve to relieve the pressure in pipe 17 by changing the initial pressure setting of said valve, as above described. An increase of pilot pressure from pipe 2'7 results in an increase of pressure in chamber 47a and a decrease of pilot pressure in a decrease of pressure in said chamber. The increase or decrease is, therefore, controlled by the degree of pressure in pipe 27.

In this manner, the force at point 3 of member 5, being determined by the sum of the forces applied at points 6 and 7, is proportional to said forces.

In the form of the invention shown in Fig. 2, the stem 32 common to cylinders 28 and 29 is extended to pass through a cylinder 49 that has an area which is selected to give a desired pressure ratio for unit 11. Said stem 32 is provided with a piston 50 that operates in cylinder 49. The pipe 27 connects cylinder 49 with the pressure relief valve 26.

It will be seen that the sum of the two pressures in cylinders 28 and 29 is elfective on piston 50, which, because of its larger area, transmits to pipe 27 a proportionally smaller hydraulic force. If the area of piston Sil is twice the lsum of the areas of pistons 30 and 31, the force in pipe 27 will be one-half the sum of the forces in cylinders 28 and 29.

The invention has been described with respect to a bank of three units to apply force on a common member, as shown, or at any three points whether or not common to the cylinders. Four or more such cylinders may comprise the bank and the hydraulic pressures in any two may be converted by the present means to produce proportional pressures in the other cylinders.

In the preferred form of the invention, the lever 36 is shown with the fulcrum in between the ends thereof, and i is, therefore, of the first kind or class of levers. Said lever may be of the second or third kind to produce greater or lesser pressures in unit 11 in substantially any degree desired.

While we have illustrated and described what we now contemplate to be the best modes of carrying out our invention, the constructions are, of course, subject to modification without departing from the spirit and scope of the invention. It is, therefore, not desired to restrict the invention to the particular forms of construction illustrated and described, but to cover all modifications that may fall within the scope of the appended claims.

Having thus described the invention, what we claim and desire to be secured by Letters Patent is:

1. Hydraulic preSsure-proportioning means comprising at least three hydraulic units, a separate conduit to conduct pressure fluid to each said unit, a pressure-settable pressure relief valve connected to one of said conduits to relieve the pressure therein, and means interconnecting the other two conduits and said relief valve to convert the sum of the pressures in said two conduits to a pressure on the relief valve to change thc pressure-relieving setting thereof.

2. Hydraulic pressure-proportioning means comprising at least three hydraulic units, a separate conduit to conduct pressure fluid to each said unit, a pressure-settable pressure relief valve connected to one of said conduits to relieve the pressure therein, a pressure-dividing apparatus connected to said other two conduits to receive the pressures thereof and convert the sum of said pressures to a proportional pressure, and means to conduct said proportional pressure to the relief valve to change the pressurerelieving setting thereof.

3. Hydraulic pressure-proportioning means according to claim 2: said apparatus comprising two cylinders each respectively connected to said two conduits, a piston in each cylinder, a common stem for said pistons, and hydraulic means connected to the relief valve and subject to the force on said stem as applied by the pressures in said two conduits to apply a setting-changing pressure on said relief valve to change the pressurerelieving setting of said relief valve.

4. Hydraulic pressure-proportioning means according to claim 2: said apparatus comprising two cylinders each respectively connected to said two conduits, a piston in each cylinder, a common stem for said pistons, and hydraulic means connected to the relief valve and subject to the force on said stern as applied by the pressure in said two conduits to apply a setting-changing pressure on said relief valve to change the pressure-relieving setting of said relief valve, the latter means comprising a third cylinder, a piston in said cylinder and a `stern on said piston, a lever having arms engaged by said two stems to transmit the force of the first-mentioned stem to the other stem to produce a pressure in the third cylinder that is proportional to the pressures in the trst two cylinders, and a conduit connecting said third cylinder and the relief valve to conduct said proportional pressure to said relief valve to change the pressure-relieving setting thereof.

5. Hydraulic pressure-proportioning means according to claim 2: said apparatus comprising two cylinders each respectively connected to said two conduits, a piston in each cylinder, a common stern for said pistons, and hydraulic means connected to the relief valve and subject to the force on said stem as applied by the pressure in said two conduits to apply a setting-changing pressure on said relief valve to change the pressure-relieving setting of said relief valve, the latter means comprising a third cylinder, a piston in said cylinder and mounted on an extension of the mentioned stem, and a conduit connecting said third cylinder and the relief valve to conduct the pressure imposed on the latter cylinder by the first two cylinders to the relief valve to change the pressure-relieving setting thereof.

6. Hydraulic pressure-proportioning means according to claim l: each said hydraulic unit being provided with a piston responsive to the respective pressures in the mentioned conduits, a member commonly connected to said pistons and subject to the force on each said piston at the respective points of connection.

References Cited in the file of this patent UNITED STATES PATENTS 2,676,638 Wheeler et al April 27, 1954 

